Quick expression evaluation

A property binding expression should evaluate quickly. Slow expression evaluation can kill your app's performance. This happens when a function performing CPU intensive work is part of an expression. Consider this binding:

<div>{{doLotsOfWork()}}</div> 

Angular will evaluate the preceding doLotsOfWork() expression every time it performs a change detection run. These change detection runs happen more often than we imagine and are based on some internal heuristics, so it becomes imperative that the expressions we use evaluate quickly.